Apparatus and method for allocating code resources to uplink ACK/NACK channels in a cellular wireless communication system

ABSTRACT

A method and apparatus are provided for allocating code resources to ACK/NACK channel indexes, when UEs need ACK/NACK transmission in a wireless communication system in which a predetermined number of orthogonal cover Walsh codes is selected from among available orthogonal cover Walsh codes, at least one subset is formed, having the selected orthogonal cover Walsh codes arranged in an ascending order of cross interference, subsets are selected for use in first and second slots of a subframe, and the orthogonal cover Walsh codes of the subset selected for each slot and ZC sequence cyclic shift values are allocated to the ACK/NACK channel indexes.

CROSS RELATED APPLICATIONS

The present application is a Continuation of U.S. patent applicationSer. No. 13/657,148 filed on Oct. 22, 2012 which in turn claims apriority to an earlier filed application Ser. No. 12/189,410 filed onAug. 11, 2008 and claims the benefit under 35 U.S.C. §119(a) of a KoreanPatent Application filed in the Korean Intellectual Property Office onAug. 10, 2007 and assigned Serial No. 2007-80943, a Korean PatentApplication filed in the Korean Intellectual Property Office on Aug. 14,2007 and assigned Serial No. 2007-82030, a Korean Patent Applicationfiled in the Korean Intellectual Property Office on Sep. 6, 2007 andassigned Serial No. 2007-90688, a Korean Patent Application filed in theKorean Intellectual Property Office on Sep. 19, 2007 and assigned SerialNo. 2007-95265, and a Korean Patent Application filed in the KoreanIntellectual Property Office on Jan. 29, 2008 and assigned Serial No.2008-9291, the entire disclosure of any of which is hereby incorporatedby reference.

BACKGROUND

1. Field of the Invention

The present invention generally relates to a cellular wirelesscommunication system. More particularly, the present invention relatesto an apparatus and method for allocating resources to controlinformation in a cellular wireless communication system.

2. Description of the Related Art

Mobile communication systems were developed to enable users to conductcommunications with mobility. The rapid development of technologies hasdriven the development of the mobile communication systems to providehigh-speed data service as well as voice service. Mobile communicationsystems have been evolving rapidly in order to meet demand forhigh-speed data service. One such example is Enhanced UniversalTerrestrial Radio Access (EUTRA), the future-generation mobilecommunication standard of the 3^(rd) Generation Partnership Project(3GPP).

Various multiple access schemes are available to mobile communicationsystems, including Time Division Multiple Access (TDMA), Code DivisionMultiple Access (CDMA), and Frequency Division Multiple Access (FDMA).Among them, CDMA is popular. However, CDMA has limitations intransmitting a large volume of data at a high rate due to a limitednumber of orthogonal codes. At present, Orthogonal Frequency DivisionMultiple Access (OFDMA) and Single Carrier-FDMA (SC-FDMA), which arespecial cases of FDMA, have been adopted as the respective DownLink (DL)and UpLink (UL) standard technologies of EUTRA.

In the EUTRA system, UL control information includesACKnowledgment/Negative ACKnowledgment (ACK/NACK) feedback informationindicating whether DL data has been received successfully and ChannelQuality Indication (CQI) information representing a DL channel state.

The ACK/NACK information is typically 1 bit and is repeatedlytransmitted to improve reception performance and expand cell coverage.In general, the CQI information occupies a plurality of bits to indicatethe channel state and is channel-encoded prior to transmission toimprove reception performance and expand cell coverage. The channelencoding is block coding, convolutional coding, or the like.

The reception reliability requirement of control information depends onthe type of the control information. An ACK/NACK requires a Bit ErrorRate (BER) of about 10⁻² to 10⁻⁴, lower than the BER requirement of aCQI, ranging from 10⁻² to 10⁻¹.

In the EUTRA system, when a User Equipment (UE) transmits only a ULcontrol information channel without data, a particular frequency band isallocated for control information transmission. A physical channeldedicated to transmission of control information only is defined as aPhysical Uplink Control Channel (PUCCH) which is mapped to the allocatedfrequency band.

With reference to FIG. 1, a PUCCH transmission structure will now bedescribed.

FIG. 1 illustrates a PUCCH transmission structure for carrying ULcontrol information in the 3GPP EUTRA system.

Referring to FIG. 1, the horizontal axis represents time and thevertical axis represents frequency. One subframe 102 is shown in thetime domain and a system transmission bandwidth 110 is shown in thefrequency domain. A basic UL transmission unit, the subframe 102 is 1ms, divided into two 0.5-ms slots 104 and 106. Each of the slots 104 and106 is composed of a plurality of SC-FDMA symbols 111 to 124 and 131 to137, or 118 to 124 and 138 to 144. In the illustrated case of FIG. 1,one slot has seven SC-FDMA symbols.

A minimum frequency unit is a subcarrier and a basic resource allocationunit is a Resource Block (RB) 108 or 109. The RBs 108 and 109 each aredefined by a plurality of subcarriers and a plurality of SC-FDMAsymbols. Herein, 12 subcarriers and 14 SC -FDMA symbols occupying twoslots form one RB, by way of example. On the DL to which OFDM isapplied, one RB is also composed of 12 subcarriers and 14 OFDM symbols.

A frequency band to which the PUCCH is mapped is the RB 108 or 109 ateither end of the system transmission bandwidth 110. Undercircumstances, a Node B can allocate a plurality of RBs for PUCCHtransmission in order to allow a plurality of users to transmit controlinformation. To increase frequency diversity during one subframe,frequency hopping may apply to the PUCCH and that frequency hopping isdone on a slot basis. Reference numerals 150 and 160 denote frequencyhopping, which will be described in more detail below.

First control information (Control #1) is transmitted in the RB 108 inthe first slot 104 and in the RB 109 in the second slot 106 by frequencyhopping. Meanwhile, second control information (Control #2) istransmitted in the RB 109 in the first slot 104 and in the RB 108 in thesecond slot 106 by frequency hopping.

In the illustrated case of FIG. 1, in the subframe 102, Control #1 iscarried in the SC-FDMA symbols 111, 113, 114, 115, 117, 138, 140, 141,142 and 144 and Control #2 is carried in the SC-FDMA symbols 131, 133,134, 135, 17, 118, 120, 121, 122 and 124. A Reference Signal (RS) istransmitted in pilot SC-FDMA symbols 112, 116, 139, 143, 132, 136, 119and 123. The pilot signal is a predetermined sequence with which areceiver performs channel estimation for coherent demodulation. Thenumber of SC-FDMA symbols carrying control information, the number of RSSC-FDMA symbols, and the positions of the SC-FDMA symbols illustrated inFIG. 1 may vary depending on the type of control information to betransmitted or depending on system implementation.

UL control information such as ACK/NACK information, CQI information,and Multiple Input Multiple Output (MIMO) feedback information fromdifferent users can be multiplexed in Code Division Multiplex (CDM). CDMis robust against interference, compared to Frequency Division Multiplex(FDM).

A Zadoff-Chu (ZC) sequence is under discussion for CDM-multiplexing ofcontrol information. Because the ZC sequence has a constant envelop intime and frequency, it has a good Peak-to-Average Power Ratio (PAPR)characteristic and exhibits excellent channel estimation performance inthe frequency domain. Also, the ZC sequence is characterized by acircular auto-correlation of 0 with respect to non-zero shift.Therefore, UEs that transmit their control information using the same ZCsequence can differentiate the control information by use of differentcyclic shift values of the ZC sequence.

In a real radio channel environment, different cyclic shift values areallocated to different users to multiplex control information, therebymaintaining orthogonality among the users. Hence, the number of multipleaccess users is determined according to the length of a ZC sequence andcyclic shift values. The ZC sequence is also applied to RS SC-FDMAsymbols and enables RSs from different UEs to be identified by use ofcyclic shift values of the ZC sequence.

In general, the length of a ZC sequence used for the PUCCH is assumed tobe 12 samples, which is equal to the number of subcarriers forming oneRB. In this case, there are up to 12 different cyclic shift values forthe ZC sequence and up to 12 PUCCHs can be multiplexed in one RB byallocating the different cyclic shift values to the PUCCHs. A TypicalUrban (TU) model being a radio channel model considered for the EUTRAsystem uses cyclic shift values of at least two-sample intervals. Thisimplies that the number of cyclic shift values is limited to 6 or lessfor one RB. As a consequence, orthogonality is maintained withoutradical loss among PUCCHs mapped to the cyclic shift values in aone-to-one correspondence.

FIG. 2 illustrates an example of multiplexing CQIs from users by use ofdifferent cyclic shift values of a ZC sequence in the same RB, when theCQIs are transmitted on PUCCHs having the configuration of FIG. 1.

Referring to FIG. 2, a vertical axis 200 represents cyclic shift valuesof the ZC sequence. Under the TU model, up to six channels can bemultiplexed in one RB without rapid loss in orthogonality. Hence, sixCQIs 202, 204, 206, 208, 210 and 212 (CQI #1 to CQI #6) are multiplexed.In the illustrated case of FIG. 2, the CQIs are transmitted using thesame ZC sequence in the same RB, while cyclic shift value ‘0’ (denotedby reference numeral 214) applies to CQI #1 from UE #1, cyclic shiftvalue ‘2’ (denoted by reference numeral 218) applies to CQI #2 from UE#2, cyclic shift value ‘4’ (denoted by reference numeral 222) applies toCQI #3 from UE #3, cyclic shift value ‘6’ (denoted by reference numeral226) applies to CQI #4 from UE #4, cyclic shift value ‘8’ (denoted byreference numeral 230) applies to CQI #5 from UE #5, and cyclic shiftvalue ‘10’ (denoted by reference numeral 234) applies to CQI #6 from UE#6.

With reference to FIG. 1, mapping between a control information signaland a ZC sequence in the ZC sequence-based CDM transmission scheme ofcontrol information will now be described.

Let a ZC sequence of length N for UE i be denoted by g(n+Δi)mod N wheren is 0, . . . , N−1, Δi denotes a cyclic shift value for UE i, and i isthe index of the UE. Also, let a control information signal to betransmitted from UE i be denoted by mi,k where k is 1, . . . , N_(sym).If N_(sym) is the number of SC-FDMA symbols used for transmission ofcontrol information in a subframe, a signal ci,k,n mapped to eachSC-FDMA symbol, i.e. an n^(th) sample of a k^(th) SC-FDMA symbol from UEi is given asci,k,n=g(n+Δi)mod N·mi,k  (1)

where k is 1, . . . , N_(sym), n is 0, . . . , N−1, and Δi denotes thecyclic shift value of UE i.

In FIG. 1, the number of SC-FDMA symbols used for transmitting controlinformation in one subframe, N_(sym) is 10, excluding four SC-FDMAsymbols for RS transmission. The ZC sequence length N is 12, equal tothe number of subcarriers forming one RB. For a single UE, a cyclicallyshifted ZC sequence is applied to each SC-FDMA symbol and a controlinformation signal to be transmitted is configured by multiplyingmodulation symbols by the time-domain cyclically shifted ZC sequence,one modulation symbol per SC-FDMA symbol allocated for controlinformation transmission. Therefore, up to N_(sym) modulation symbols ofcontrol information can be transmitted in one subframe. That is, up to10 control information modulation symbols can be transmitted in the onesubframe illustrated in FIG. 1.

The multiplexing capacity of PUCCHs that deliver control information canbe increased by adding time-domain orthogonal covers to the above ZCsequence-based CDM transmission scheme of control information. A majorexample of the orthogonal covers is Walsh sequences. For orthogonalcovers of length M, there are M sequences that satisfy orthogonalitybetween them. Specifically, time-domain orthogonal covers apply toSC-FDMA symbols to which 1-bit control information like an ACK/NACK ismapped, thus increasing the multiplexing capacity. In the EUTRA system,use of three SC-FDMA symbols per slot is considered for RS transmissionon a PUCCH that delivers an ACK/NACK in order to improve the performanceof channel estimation. Therefore, when one slot has seven SC-FDMAsymbols, as illustrated in FIG. 1, four SC-FDMA symbols are availablefor ACK/NACK transmission. The use of the time-domain orthogonal coversis limited to one slot or less, to thereby minimize the loss oforthogonality caused by changes in a radio channel. An orthogonal coverof length 4 is applied to the four SC-FDMA symbols for ACK/NACKtransmission, while an orthogonal cover of length 3 is applied to thethree SC-FDMA symbols for RS transmission. Users that transmitACKs/NACKs and RSs are basically identified by their cyclic shift valuesof a ZC sequence and further identified by their orthogonal covers.Since RSs mapped to ACKs/NACKs in a one-to-one correspondence arerequired for coherent ACK/NACK reception, the multiplexing capacity ofACK/NACK signals is limited by the RSs. For instance, if up to sixcyclic shift values are available in one RB under the TU channel model,a different time-domain orthogonal cover of length 3 can be applied toeach cyclic shift value of a ZC sequence used for an RS. As a result,RSs from up to 18 different users can be multiplexed. Considering thatACKs/NACKs correspond to RSs one to one, up to 18 ACKs/NACKs can bemultiplexed in one RB. In this case, four orthogonal covers of length 4are available for ACKs/NACKs and three of them are used. The orthogonalcovers applied to the ACKs/NACKs are known to both the Node B and the UEby a preliminary agreement or signaling. The use of time-domainorthogonal covers can increase the multiplexing capacity by three times,compared to non-use of time-domain orthogonal covers.

FIG. 3 illustrates an example of multiplexing ACKs/NACKs from users inthe same RB by use of different cyclic shift values of a ZC sequence andadditional time-domain orthogonal covers in the above-described PUCCHstructure for ACK/NACK transmission.

Referring to FIG. 3, a vertical axis 300 represents cyclic shift valuesof the ZC sequence and a horizontal axis 302 represents time-domainorthogonal covers. In the TU model, up to six channels can bemultiplexed in one RB without rapid loss in orthogonality and threeorthogonal covers 364, 366 and 368 of length 4 are additionally used.Hence, up to 18 (6×3) ACKs/NACK channels 304, 306, 308, 310, 312, 314,316, 318, 320, 322, 324, 326, 328, 330, 332, 334, 336 and 338 (ACK/NACK#1 to ACK/NACK #18) can be multiplexed. In the illustrated case of FIG.3, the ACKs/NACKs are transmitted using the same ZC sequence in the sameRB. For the ACK/NACK transmission, cyclic shift value ‘0’ (denoted byreference numeral 340) and orthogonal cover ‘0’ (denoted by referencenumeral 364) apply to ACK/NACK #1 from UE #1, cyclic shift value ‘0’(denoted by reference numeral 340) and orthogonal cover 1′ (denoted byreference numeral 366) apply to ACK/NACK #2 from UE #2, and the cyclicshift value ‘0’ (denoted by reference numeral 340) and orthogonal cover‘2’ (denoted by reference numeral 368) apply to ACK/NACK #3 from UE #3.In this manner, cyclic shift value ‘10’ (denoted by reference numeral360) and orthogonal cover ‘0’ (denoted by reference numeral 364) applyto ACK/NACK #16 from UE #16, cyclic shift value ‘10’ (denoted byreference numeral 360) and orthogonal cover ‘1’ (denoted by referencenumeral 366) apply to ACK/NACK #17 from UE #17, and cyclic shift value‘10’ (denoted by reference numeral 360) and orthogonal cover ‘2’(denoted by reference numeral 368) apply to ACK/NACK #18 from UE #18.The orthogonal covers 364, 366 and 368 are orthogonal codes of length 4that are mutually orthogonal.

The transmission signal format of ACK/NACK channels illustrated in FIG.3 is detailed in FIG. 4.

FIG. 4 illustrates a transmission format for transmitting ACK/NACK #5and ACK/NACK #16 in one slot. Referring to FIG. 4, W_(i) 32 [W_(i,0)W_(i,1) W_(i,2) W_(i,3)] where i=0, . . . , 3 can be a Walsh code oflength 4 generated from a Walsh-Hadamard matrix given as

$\begin{matrix}{\begin{bmatrix}W_{0} \\W_{1} \\W_{2} \\W_{3}\end{bmatrix} = \begin{bmatrix}{+ 1} & {+ 1} & {+ 1} & {+ 1} \\{+ 1} & {- 1} & {+ 1} & {- 1} \\{+ 1} & {+ 1} & {- 1} & {- 1} \\{+ 1} & {- 1} & {- 1} & {+ 1}\end{bmatrix}} & (2)\end{matrix}$

D_(i)=[D_(i,0) D_(i,1) D_(i,2)] where i=0, . . . ,2 can be a Fouriersequence of length 3 expressed as

$\begin{matrix}{\begin{bmatrix}D_{0} \\D_{1} \\D_{2}\end{bmatrix} = \begin{bmatrix}{+ 1} & {+ 1} & {+ 1} \\{+ 1} & {\mathbb{e}}^{j\frac{\pi}{3}} & {\mathbb{e}}^{j\frac{\pi}{3}} \\{+ 1} & {\mathbb{e}}^{j\frac{\pi}{3}} & {\mathbb{e}}^{j\frac{\pi}{3}}\end{bmatrix}} & (3)\end{matrix}$

For example, ACK/NACK symbol b of ACK/NACK channel #5 is multiplied by asequence 405 [s3, s4, . . . , s12, s1, s2] resulting from cyclicallyshifting a ZC sequence of length 12 [s1, s2, . . . , s12] by two samplesand repeated in SC-FDMA symbols 401 to 404. Then the multipliedsequences are again multiplied by the Walsh sequence chips W_(1,0),W_(1,1), W_(1,2), W_(1,3) of the orthogonal cover ‘1’ in the SC-FDMAsymbols 401 to 404. Meanwhile, ACK/NACK symbol b of ACK/NACK channel #16is multiplied by a sequence 415 [s11, s12, s1 . . . , s9, s10] resultingfrom cyclically shifting the ZC sequence of length 12 [s1, s2, . . . ,s12] by ten samples and repeated in SC-FDMA symbols 411 to 414. Then themultiplied sequences are again multiplied by the Walsh sequence chipsW_(0,0), W_(0,1), W_(0,2), W_(0,3) of orthogonal cover ‘0’ in theSC-FDMA symbols 411 to 414.

Although orthogonality is well preserved among orthogonal cover codes ifa channel experiences weak fading, the orthogonality may be lost when aUE moves fast and thus the level of a signal received in one slotfluctuates greatly between SC-FDMA symbols due to time selective fading.Then interference occurs between ACK/NACK channels to which the samecyclic shift value is applied. For example, if UE #1 that transmitsACK/NACK #1 moves fast in FIG. 3, the signal of ACK/NACK #1 interfereswith ACKs/NACKs #2 and #3 from other UEs, thereby degrading thereception performance of ACKs/NACKs #2 and #3.

SUMMARY OF THE INVENTION

Accordingly, exemplary embodiments of the present invention provide anapparatus and method for allocating resources to ACK/NACK channels tominimize cross interference between the ACK/NACK channels even in a fastmoving environment, in the case where the ACK/NACK channels aremultiplexed further with Walsh codes as time-domain orthogonal covers ina system in which ACK/NACK channels are transmitted, being multiplexedin the same frequency resource by use of cyclic shifts of a ZC sequence.

Other exemplary embodiments of the present invention provide anapparatus and method for performing orthogonal cover hopping to minimizethe effects of an inter-cell interference and a fast movement of a UEthat causes interference, when Walsh codes applied to ACK/NACK channelsare changed between slots, that is, orthogonal cover hopping occurs.

Further, exemplary embodiments of the present invention provide a methodfor allocating orthogonal cover resources so as to minimize the effectsof a fast movement of a UE that caused interference, even whenorthogonal cover hopping does not occur.

Exemplary embodiments of the present invention provide a method forallocating code resources to ACK/NACK channel indexes, when UEs requireACK/NACK transmission in a wireless communication system, comprising:selecting a predetermined number of orthogonal cover Walsh codes fromamong available orthogonal cover Walsh codes; forming at least onesubset from the selected number of orthogonal cover Walsh codes;arranging in an ascending order of cross interference the selectedorthogonal cover Walsh codes; selecting subsets of the arranged Walshcodes for use in first and second slots of a subframe; and allocatingthe orthogonal cover Walsh codes of the selected subset for each slotand ZC sequence cyclic shift values to the ACK/NACK channel indexes.

In accordance with other exemplary embodiments of the present invention,there is provided an apparatus for allocating resources to ACK/NACKchannels of a UE in a wireless communication system, comprising: anACK/NACK symbol generator that generates an ACK/NACK symbol; anorthogonal cover symbol generator that selects subsets, for use in firstand second slots of a subframe, from at least one subset formed byselection of a predetermined number of orthogonal cover Walsh codes fromamong available orthogonal cover Walsh codes and arrangement of theselected orthogonal cover Walsh codes in an ascending order of crossinterference, and generation of an orthogonal cover sequence symbol tobe mapped to an ACK/NACK channel that will transmit ACK/NACKinformation; a first multiplier that multiplies the ACK/NACK symbol bythe orthogonal cover sequence symbol; a multiplexer that outputs themultiplied ACK/NACK symbol and a generated RS symbol each at apredetermined symbol timing; a second multiplier that multiplies asignal received from the multiplexer by a ZC sequence; and a subcarriermapper that allocates the signal received from the second multiplier toa band set for transmission of the control information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of certain exemplaryembodiments of the present invention will be more apparent from thefollowing detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates the structure of a EUTRA UL control channel;

FIG. 2 illustrates an exemplary multiplexing structure of EUTRA UL CQIchannels;

FIG. 3 illustrates an exemplary multiplexing structure of EUTRA ULACK/NACK channels;

FIG. 4 illustrates an exemplary subframe structure of EUTRA UL ACK/NACKchannels;

FIG. 5a is a graph illustrating the computer-aided simulation results ofthe Cumulative Distribution Function (CDF) of cross interference in thecase where Walsh codes are used as orthogonal covers for EUTRA ULACK/NACK channels;

FIG. 5b is a table showing subsets of Walsh codes made according to thesimulation results of FIG. 5 a;

FIG. 6 illustrates a method for allocating resources to ACK/NACKchannels according to an exemplary embodiment of the present invention;

FIG. 7 illustrates a method for allocating resources to ACK/NACKchannels according to another exemplary embodiment of the presentinvention;

FIG. 8 illustrates a method for allocating resources to ACK/NACKchannels according to a third exemplary embodiment of the presentinvention;

FIG. 9 illustrates another method for allocating resources to ACK/NACKchannels according to the third exemplary embodiment of the presentinvention;

FIG. 10 illustrates a method for allocating resources to ACK/NACKchannels according to a fourth exemplary embodiment of the presentinvention;

FIG. 11 illustrates a method for allocating resources to ACK/NACKchannels according to a fifth exemplary embodiment of the presentinvention;

FIG. 12 illustrates a method for allocating resources to ACK/NACKchannels according to a sixth exemplary embodiment of the presentinvention;

FIG. 13 illustrates another method for allocating resources to ACK/NACKchannels according to the sixth exemplary embodiment of the presentinvention;

FIG. 14 illustrates a method for allocating resources to ACK/NACKchannels according to a seventh exemplary embodiment of the presentinvention;

FIG. 15 is a block diagram illustrating a transmitter of a UE accordingto an exemplary embodiment of the present invention;

FIG. 16 is a flowchart illustrating a transmission method of the UEaccording to an exemplary embodiment of the present invention;

FIG. 17 is a block diagram illustrating a receiver of a Node B accordingto an exemplary embodiment of the present invention;

FIG. 18 is a flowchart illustrating a reception method of the Node Baccording to an exemplary embodiment of the present invention; and

FIG. 19 is a block diagram illustrating an apparatus for generating anorthogonal code subset hopping pattern according to the fourth exemplaryembodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features and structures.

DETAILED DESCRIPTION OF THE INVENTION

The matters defined in the description such as a detailed constructionand elements are provided to assist in a comprehensive understanding ofexemplary embodiments of the invention. Accordingly, those of ordinaryskill in the art will recognize that various changes and modificationsof the embodiments described herein can be made without departing fromthe scope and spirit of the invention. For the purposes of simplicity,descriptions of well-known functions and constructions are omitted forclarity and conciseness.

The present invention provides a method for designing an orthogonalcover hopping pattern for ACK/NACK channel transmission, when anorthogonal cover applied to an ACK/NACK channel by a UE changes betweenslots, that is, orthogonal cover hopping occurs. Also, the presentinvention provides a method for allocating resources to ACK/NACKchannels when orthogonal cover hopping does not occur between slots.

Orthogonal cover hopping of ACK/NACK channels between slots has theeffect of randomizing interference from ACK/NACK channels transmittedfrom neighbor cells in the same frequency band and randomizinginterference between ACK/NACK channels within a current cell, caused bya UE's fast movement.

FIG. 5a illustrates the CDF of cross interference among the Walsh codesdescribed in equation (2) in the case where a UE moves at 360 km/h overa single-path Rayleigh fading channel.

Referring to FIG. 5, R(i, j) denotes the cross interference betweenWalsh codes W_(i) and W_(j). As noted from the graph of FIG. 5a , crossinterference varies depending on Walsh codes. For example, R(0, 3)representing the cross interference between Walsh codes, W₀ and W₃ isless than level 0.1 at a CDF of 90%. This implies that when the UE movesat 360 km/h and thus a channel experiences fading, the interferencelevel between W₀ and W₃ is 10% (i.e. 0.1) of a maximum interferencelevel of 1, when the CDF is 90%. On the other hand, R(0, 2) representingthe cross interference between Walsh codes, W₀ and W₂ is around 0.75,higher than R(0, 3) at the CDF of 90%.

If three Walsh codes are used for ACK/NACK channel transmission in oneslot as illustrated in FIG. 3, the subsets shown in FIG. 5b of Walshcodes can be made according to the simulation results of FIG. 5 a.

As shown in FIG. 5b , each of the Walsh codes of the Best columninterferes least with the other Walsh codes in its subset, referring tothe CDF results of interference illustrated in FIG. 5. The Walsh codesof the 2^(nd) Best column cause stronger interference than those of theBest column but weaker interference than those of the Worst column intheir subsets. The Walsh codes of the Worst column cause the strongestinterference in their subsets. Hereinbelow, the Walsh codes of the Best,2^(nd) Best, and Worst columns are referred to as Code A, Code B andCode C in their subsets, respectively.

A comparison in cross interference among the Walsh codes of subset 2,W0, W2 and W3 tells that W3 being Code A has a far smaller crossinterference than 0.2 at the CDF of 90%, with respect to both W2 and W0.On the other hand, W2 being Code C in subset 2 has a cross interferenceclose to 0.75 at the CDF of 90%, with respect to W0. W0 being Code B insubset 2 has a cross interference close to 0.75 at the CDF of 90%, withrespect to W2 but a cross interference less than 0.1 at the CDF of 90%with respect to W3. Based on the Walsh code subsets listed in Table 1,the present invention provides a method for allocating Walsh coderesources to ACK/NACK channels and performing code hopping for theACK/NACK channels to improve reception performance by randomizinginterference between the ACK/NACK channels in a fast-moving UEenvironment.

The classification of the Walsh codes in subset 2 illustrated in Table 1coincides with a conclusion reached by R1-072857 “Coherent UplinkACK/NACK Transmission with High Speed UEs” Texas Instrument, Jun. 25,2007) submitted to 3GPP RAN TSG Working Group 1, which is incorporatedby reference herein. Although the R1-072857 document discusses onlysubset 2, the present invention can classify Walsh codes into Best,2^(nd) Best, and Worst in four subsets as done for subset 2. The crossinterference levels of the Walsh codes in each subset are the sameirrespective of the subsets, which are observed in FIG. 5. In otherwords, the cross interferences among Code A, Code B and Code C are thesame in every subset.

Now a description will be made of a method and apparatus fortransmitting and receiving ACK/NACK channels according to exemplaryembodiments of the present invention.

Regarding allocation of code resources to ACK/NACK channels, variousembodiments can be realized depending on the following conditions.

-   -   (1) Whether different subsets are used in two slots forming one        subframe by subset hopping;    -   (2) Whether orthogonal cover Walsh code hopping occurs between        two slots forming one subframe (two cases of orthogonal code        hopping can be considered as illustrated in FIGS. 6 and 7); and    -   (3) Whether the sequence of ZC sequence cyclic shift values        allocated to ACK/NACK channels in a first slot changes randomly        in a second slot.

While embodiments of the present invention that can be realized bycombining the above conditions are described below, it is clear thatother embodiments achieved by combining the above conditions fall withinthe scope of the present invention.

FIG. 6 illustrates a method for allocating resources to ACK/NACKchannels and an orthogonal cover Walsh code hopping pattern betweenslots according to first exemplary embodiments of the present invention.The allocation of ZC sequence cyclic shift values to ACK/NACK channelsillustrated in FIG. 6 is based on R1072799 technical document “Usage ofCyclic Shifts and Blockwise Spreading Codes for Uplink ACK/NACK”,Panasonic, Jun. 25, 2007, of 3GPP RAN TSG Working Group 1,which isincorporated by reference herein.

A description will be provided below of a method for allocatingorthogonal cover Walsh codes to ACK/NACK channels using the subsets ofTable 1 formed based on the CDF results of FIG. 5 in accordance withfirst exemplary embodiments of the present invention.

Referring to FIG. 6, the Walsh codes of a column 604 are allocated toACK/NACK channels in the first slot of a subframe and the Walsh codes ofa column 605 are allocated to ACK/NACK channels in the second slot ofthe subframe. ACK/NACK #0 denoted by reference numeral 630 representsACK/NACK channel #0. For convenience' sake, the other ACK/NACK channelsare represented by their indexes as noted from #12 representing ACK/NACKchannel #12 denoted by reference numeral 631. There is no need forallocating ACK/NACK channel indexes in the same pattern as shown in FIG.6. Rather, it is important to decide what ZC sequence cyclic shiftvalues and what Walsh code resources to use for ACK/NACK channeltransmission. In other words, ACK/NACK #0 may exchange places withanother ACK/NACK channel.

As proposed in the R1-072799 technical document “Usage of Cyclic Shiftsand Blockwise Spreading Codes for Uplink ACK/NACK (Panasonic, Jun. 25,2007) of 3GPP RAN TSG Working Group 1, two ACK/NACK channels areallocated to each of ZC sequences with even cyclic shift values 610,612, 614, 616, 618 and 620 and one ACK/NACK channel is allocated to eachof ZC sequences with odd cyclic shift values 611, 613, 615, 617, 619 and621.

An important feature of the allocation of Walsh codes to ACK/NACKchannels illustrated in FIG. 6 is that Code A having the best crossinterference characteristic is allocated to only the ACK/NACK channelstransmitted using the ZC sequences with the even cyclic shift values610, 612, 614, 616, 618 and 620, each of which is allocated to twoACK/NACK channels. For example, in the case of ACK/NACK channelsallocated to cyclic shift value 0, Code A 601 is allocated to ACK/NACK#0 in the first slot 604 and Code A 608 is allocated to ACK/NACK #12 inthe second slot 605. Similarly, Code B is allocated to the ACK/NACKchannels using the ZC sequences with the even cyclic shift values 610,612, 614, 616, 618 and 620. The reason for allocating Walsh codes havinggood cross interference characteristics to ACK/NACK channels using theZC sequences each of which is allocated to two ACK/NACK channels is thatinterference between ACK/NACK channels using the same cyclic shift valueis more severe than interference between ACK/NACK channels usingdifferent cyclic shift values. Hence, when orthogonal cover hoppingoccurs to Code A and Code B between the first and second slots, Code Aand Code B are exchanged between different ACK/NACK channels using thesame cyclic shift value. For instance, Code A and Code B are alternatelyused for ACK/NACK #0 and ACK/NACK #12 in the first and second slots byorthogonal cover hopping. The orthogonal cover hopping between slotsrandomizes interference between neighbor cells and randomizesorthogonality loss between ACK/NACK channels caused by fast movement ofa UE. Meanwhile, Code C having the worst cross interferencecharacteristic is allocated to ACK/NACK channels with cyclic shiftvalues each of which is allocated to one ACK/NACK channel. For theseACK/NACK channels, orthogonal cover hopping does not occur betweenslots. Since Code C causes strong cross interference relative to Code Aand Code B, it is allocated to ACK/NACK channels with cyclic shiftvalues each being allocated to a single ACK/NACK channel, to therebyprevent cross interference.

The above-described orthogonal code resource allocation method will bemore detailed, taking the case where subset 0 of Table 1 is used forACK/NACK channel transmission. Referring to FIG. 6, orthogonal codehopping occurs for the ACK/NACK channels with cyclic shift value 0 byallocating W1 being Code A in subset 0 alternately to ACK/NACK #0 andACK/NACK #12 in the first and second slots. W2 being Code B in subset 0is allocated alternately to ACK/NACK #12 and ACK/NACK #0 in the firstand second slots. W0 being Code C in subset 0 is dedicated to ACK/NACK#6 with cyclic shift value 1 adjacent to cyclic shift value 0. Theorthogonal cover Walsh codes of the other subsets are allocated toACK/NACK channels according to Table 1 and FIG. 6.

The case where orthogonal cover hopping occurs between slots has beendescribed above. Without orthogonal cover hopping, one of the orthogonalcover allocations in the first and second slots 604 and 605 applies toboth the slots 604 and 605. While it is assumed in FIG. 6 that 12 cyclicshift values available in one RB are used for ACK/NACK channeltransmission, to which the present invention is not limited, some of thecyclic shift values can be allocated to control channels other thanACK/NACK channels, such as CQI channels.

FIG. 7 illustrates a method for allocating resources to ACK/NACKchannels according to second exemplary embodiments of the presentinvention. As in the first exemplary embodiments of the presentinvention illustrated in FIG. 6, this resource allocation methodallocates Walsh code resources when the three Walsh codes of a subsetare used as orthogonal covers for ACK/NACK channel transmission.

As in the first exemplary embodiments of the present inventionillustrated in FIG. 6, Code A is used for ACK/NACK channels using cyclicshift values each of which is allocated to two ACK/NACK channels andorthogonal code hopping occurs between the two channels on a slot basis.Compared with the first exemplary embodiment of the present invention,Code C is used for ACK/NACK channels with odd cyclic shift values in thefirst slot, and is allocated to ACK/NACK channels that used Code A inthe first slot, in the second slot.

To be more specific, for example, in FIG. 7 ACK/NACK #0 uses Code A inthe first slot as indicated by reference numeral 706 and uses Code C inthe second slot as indicated by reference numeral 708. ACK/NACK #12using the same cyclic shift value as ACK/NACK #0 uses code B asindicated by reference numeral 707 in the first slot and uses Code A asindicated by reference numeral 709 in the second slot. ACK/NACK #6 witha cyclic shift value one offset apart from the cyclic shift value ofACK/NACK #0 and ACK/NACK #12 uses Code C in the first slot as indicatedby reference numeral 710 and uses Code B in the second slot as indicatedby reference numeral 711.

Compared to the first exemplary embodiments of the present invention,the second exemplary embodiments of the present invention performsorthogonal cover hopping ACK/NACK channels using Code C on a slot basis,thus further randomizing inter-cell interference. Even though Code Chops to ACK/NACK channels using cyclic shift values each of which isallocated to two ACK/NACK channels, Code A still hops only between theACK/NACK channels using the cyclic shift values each of which isallocated to two ACK/NACK channels. As noted from FIG. 5, if Code B andCode C are used for ACK/NACK channels using the same cyclic shift value,cross interference gets very severe and thus performance degradesgreatly in a fast moving environment. Yet, the cross interferencebetween Code A and Code C is very small, 0.2 or less at a CDF of 90% inFIG. 5. The first and second exemplary embodiments of the presentinvention both employ one subset in two slots.

Now a description will be made of a method for allocating orthogonalcode resources to ACK/NACK channels when different subsets are used intwo slots according to third exemplary embodiments of the presentinvention.

Third exemplary embodiments of the present invention provide a methodfor allocating orthogonal code resources to ACK/NACK channels whendifferent subsets are used in the first and second slots. The use ofdifferent subsets in the first and second slots, i.e. subset hoppingfurther enhances the effects of randomization of inter-cellinterference.

Referring to FIG. 8, the Walsh codes of subset i are used in the firstslot, whereas the Walsh codes of subset k are used in the second slot.Aside from subset hopping between slots, the third exemplary embodimentsof the present invention perform orthogonal cover hopping in the samemanner as in the first exemplary embodiments of the present invention.

That is, for example, ACK/NACK #0 uses Code A of subset i in the firstslot and Code B of subset k in the second slot. Similarly, ACK/NACK #12uses Code B of subset i in the first slot and Code A of subset k in thesecond slot. ACK/NACK #6 uses Code C in the two slots, Code C of thefirst slot being from subset i and Code C of the second slot being fromsubset k. Thus, when the Walsh codes of subset 0 apply to the first slotand the Walsh codes of subset 1 apply to the second slot, W0 and W1apply as orthogonal covers to ACK/NACK #0 in the first and second slots,respectively, referring to the column Code C of Table 1.

Meanwhile, fourth embodiments provide a method for allocating orthogonalcover resources to ACK/NACK channels illustrated in FIG. 9 is anextension of the orthogonal cover resource allocation scheme illustratedin FIG. 7 according to the third exemplary embodiments of the presentinvention. The orthogonal cover resource allocation of FIG. 9 differsfrom the orthogonal cover resource allocation of FIG. 7 in that subsethopping takes place between slots such that the Walsh codes of subset iare used in the first slot and the Walsh codes of subset k are used inthe second slot. Therefore, Code A of subset i applies to ACK/NACK #0 inthe first slot and Code C of subset k applies to ACK/NACK #0 in thesecond slot. ACK/NACK #12 with the same cyclic shift value as ACK/NACK#0 uses Code B of subset i in the first slot and Code A of subset k inthe second slot. ACK/NACK #6 transmitted alone with a cyclic shift valueone offset apart from the cyclic shift value of ACK/NACK #0 and ACK/NACK#12 uses Code C of subset i in the first slot and Code B of subset k inthe second slot.

Third and fourth exemplary embodiments of the present invention are thesame in that different subsets are used in the first and second slotsand differ in that subset hopping takes place between slots withoutorthogonal code hopping in fourth exemplary embodiments of the presentinvention.

Referring to FIG. 10, ACK/NACK #0 uses Code A in the two slots, andACK/NACK #12 and ACK/NACK #6 use Code B and Code C, respectively in thetwo slots. In the case where subset 0 applies to the first slot andsubset 1 applies to the second slot, ACK/NACK #0 uses W1 and W0 asorthogonal covers in the first and second slots, respectively accordingto the column Code A of Table 1. This orthogonal cover resourceallocation method aims at randomization of inter-cell interference, notrandomization of interference between ACK/NACK channels caused by fastUE movement.

If a Node B can estimate the velocity of each UE and allocate anACK/NACK channel with Code A to a fast UE, the effects of interferencecan be reduced, compared to allocation of Code A to different ACK/NACKchannels in different slots. That is, when the Node B cannot allocateACK/NACK channels to UEs according to their velocities, the ACK/NACKorthogonal cover resource allocation methods using orthogonal coverhopping according to the first, second and third exemplary embodimentsof the present invention are more efficient. Yet, if the Node B canallocate Code A to a fast UE according to its velocity, the fast UE isallowed to keep using Code A in the two slots, thus reducing the effectsof interference on other ACK/NACK channels. Also, since differentsubsets are used in different slots, the randomization of inter-cellinterference can be achieved in fourth exemplary embodiments as in thepreviously discussed other exemplary embodiments of the presentinvention.

Regarding the subsets listed in Table 1, use of different subsets forACK/NACK transmission in different cells can randomize inter-cellinterference. For example, when four neighbor cells use subsets 0, 1, 2and 3 of Table 1 or randomly selected subsets and UEs within the cellstransmit ACK/NACK channels using their subsets according to theorthogonal code allocation schemes illustrated in FIGS. 6 to 9, theinter-cell interference randomization is achieved. In the resourceallocation schemes illustrated in FIGS. 8 and 10, the inter-cellinterference randomization can be realized by applying subset hoppingpatterns to cells randomly.

For instance, FIG. 19 illustrates a Gold scrambling sequence generatorthat was designed for transmitting a data channel or a control channellike a CQI channel and that is now utilized for generating an orthogonalcover hopping pattern.

Referring to FIG. 19, a Gold sequence 1905 is generated by XOR-operatingbinary sequences 1906 and 1907 output from two m-sequence generators1901 and 1902. The Gold sequence generator applies a random sequence toeach cell because a sequence generation controller 1900 sets an initialsequence according to a cell Identifier (ID). A cell-specific orthogonalcode subset hopping pattern is acquired by converting two bits of thebinary sequences 1906 and 1907 to a value ranging from 0 to 3 in a 4-arynumber converter 1903 and selecting one of the four subsets listed inTable 1 according to the value in every slot. The m-sequence generators1901 and 1902 can share the sequence generator used for scrambling dataand a control channel or use a different device from the scrambling codegenerator, for the purpose of generating an orthogonal code hoppingpattern.

ACK/NACK channels change their cyclic shift values of a ZC sequence usedin the first slot to random ones in the second slot in fifth exemplaryembodiments of the present invention.

Referring to FIG. 11, ACKs/NACKs #0, 1, 2, 3, 4 and 5 using Code A ofsubset i are mapped to cyclic shift values 0, 2, 4, 6, 8 and 10 in thefirst slot and ACKs/NACKs #1, 3, 5, 0, 2 and 4 using Code B of subset kare mapped to the cyclic shift values 0, 2, 4, 6, 8 and 10 in the secondslot. Similarly, ACK/NACK channels using Code B or Code C of subset i inthe first slot use different cyclic shift values in the second slot fromthe cyclic shift values used in the first slot and the sequence ofACK/NACK channels mapped to the cyclic shift values is also changed inthe second slot. That is, ACK/NACK channels using Code C in the secondslot are allocated to the cyclic shift values 0 to 11 in the order ofACKs/NACKs #10, 7, 9, 11, 6 and 8. ACK/NACK channels using Code A in thesecond slot are allocated to the cyclic shift values 0 to 11 in theorder of ACKs/NACKs #15, 17, 12, 14, 16 and 13. The ACK/NACKtransmission scheme illustrated in FIG. 8 is the same as thatillustrated in FIG. 11 in that orthogonal covers mapped to ACK/NACKchannels hop between slots, but differs from that illustrated in FIG. 11in that cyclic shift values change to a random pattern in the secondslot for ACK/NACK channels using the same orthogonal cover.

Similarly to the first through fourth exemplary embodiments of thepresent invention, Code A of the subsets listed in Table 1 is alwaysallocated to one of two ACK/NACK channels allocated to the same cyclicshift value. It is because Code A can minimize fast UE-caused crossinterference between ACK/NACK channels.

A sixth exemplary embodiment of the present invention illustrated inFIG. 12 is very similar to the third exemplary embodiment of the presentinvention illustrated in FIG. 9. That is, in the second slot, ACKs/NACKs#0 to 5 use Code C of subset k, ACKs/NACKs #6 to 11 use Code B of subsetk, and ACKs/NACKs #12 to 17 use Code A of subset k. However, ACKs/NACKs#0 to 5 are mapped to even cyclic shift values in the first slot and oddcyclic shift values in the second slot, and ACKs/NACKs #6 to 11 aremapped to odd cyclic shift values in the first slot and even cyclicshift values in the second slot. That is, in addition to orthogonalcover hopping, cyclic shift values are changed between slots. In otherwords, although the first and second slots use the same combination oforthogonal cover codes selected from entire code resources and the samecombination of cyclic shift values, ACK/NACK channels using the coderesources change between the two slots. For instance, ACK/NACK #6 andACK/NACK #0 are allocated to code resources corresponding to Code C andcyclic shift value 1 in the first and second slots, respectively.

Meanwhile, an ACK/NACK transmission scheme illustrated in FIG. 13further uses the above-described cyclic shift hopping in addition to theACK/NACK transmission scheme illustrated in FIG. 11. In FIG. 13, besidesrandom cyclic shift hopping and orthogonal code hopping, ACKs/NACKs #6to 11 are allocated to odd cyclic shift values in the first slot and toeven cyclic shift values in the second slot, and ACKs/NACKs #12 to 15are allocated to even cyclic shift values in the first slot and to oddcyclic shift values in the second slot.

In the above exemplary embodiments of the present invention, subset i ofthe first slot and subset k of the second slot may be identical, towhich the present invention is not limited. In accordance with a seventhexemplary embodiment of the present invention, ACK/NACK channelstransmitted with the same orthogonal code in the first slot can betransmitted in the second slot by random orthogonal code hopping andrandom cyclic shift hopping.

In seventh exemplary embodiments and referring to FIG. 14, ACKs/NACKs #0to 5 use the same Code A in the first slot and hop randomly to Code A,Code B and Code C in the second slot, compared to the previous exemplaryembodiments of the present invention in which ACKs/NACKs #0 to 5 hop tothe same orthogonal codes in the second slot. The random orthogonal codehopping occurs also to ACKs/NACKs #6 to 11 and #12 to 17. Despite therandom orthogonal code hopping and the random cyclic shift hopping, CodeA of subsets is always allocated to ACK/NACK channels with cyclic shiftvalues each of which is allocated to two ACK/NACK channels. As statedbefore, Code A causes less interference than any other orthogonal code.

FIG. 15 is a block diagram of a UE transmitter according to an exemplaryembodiment of the present invention.

Referring to FIG. 15, an ACK/NACK symbol generator 1500 generatesACK/NACK symbols to be transmitted. An orthogonal cover symbol generator1511 generates orthogonal cover sequence symbols mapped to an ACK/NACKchannel that will carry the ACK/NACK information. Under the control of ahopping controller 1510, the orthogonal cover symbol generator 1511 cangenerate different orthogonal covers for first and second slots. Amultiplier 1012 multiplies the ACK/NACK symbols by the orthogonal coversymbols. A multiplexer (MUX) 1003 outputs a multiplied ACK/NACK symbolor an RS symbol at an SC-FDMA symbol timing as illustrated in FIG. 4 toa ZC sequence multiplier 1506. The ZC sequence multiplier 1506multiplies the received ACK/NACK symbol or RS symbol by a ZC sequence.Like the ACK/NACK symbol, the RS symbol is also multiplied by an RSorthogonal cover corresponding to the index of the ACK/NACK channel. AFast Fourier Transform (FFT) processor 1007 processes the symbolreceived from the ZC sequence multiplier 1006 by FFT. A subcarriermapper 1508 maps the FFT signals to subcarriers corresponding to afrequency band allocated to the control information. Under the controlof the hopping controller 1510, the subcarrier mapper 1508 maps FFTsignals to subcarriers corresponding to an opposite frequency band, fortransmission in the second slot as illustrated in FIG. 1. An InverseFast Fourier Transform (IFFT) processor 1509 processes the mappedsubcarrier signals by IFFT.

FIG. 16 is a flowchart illustrating a transmission method of a UEaccording to an exemplary embodiment of the present invention.

Referring to FIG. 16, the UE acquires ACK/NACK channel configurationinformation on a common control channel for transmitting systeminformation, or by higher signaling information. When the UE establishesa call setup with a cell or needs to transmit an ACK/NACK, the ACK/NACKchannel configuration information is acquired.

In step 1601, the UE determines whether an ACK/NACK is to be transmittedin a current subframe. A main event requiring ACK/NACK transmission isreception of a data channel from a Node B. If the ACK/NACK informationis to be transmitted in step 1601, the UE acquires the index of anACK/NACK channel to deliver an ACK/NACK symbol in step 1602. TheACK/NACK channel information can be received explicitly from the Node Bor acquired implicitly from a DL control channel or a data channel. TheUE selects an orthogonal cover sequence index and a ZC sequence cyclicshift value according to the ACK/NACK channel configuration informationand the ACK/NACK channel index information in step 1603. As describedabove, step 1603 can be performed in accordance with one of the sevenexemplary embodiments of the present invention. In step 1604, the UEtransmits the ACK/NACK symbol using the orthogonal cover sequence and aZC sequence cyclically shifted by the cyclic shift value.

FIG. 17 is a block diagram of a Node B receiver according to anexemplary embodiment of the present invention.

An FFT processor 1709 processes a received signal by FFT. A subcarrierdemapper 1708 selects FFT subcarrier signals corresponding to anACK/NACK channel transmission band of a target UE. A ZC sequencecorrelator 1206 correlates the FFT subcarrier signals with a ZC sequenceapplied to a current symbol and provides the resulting signal to an IFFTprocessor 1707. The output of the IFFT 1707 is provided to a DEMUX 1703.If a current SC-FDMA symbol index indicates an RS symbol, the DEMUX 1703outputs the RS symbol to an RS symbol de-coverer 1701. The RS symbolde-coverer 1701 de-covers an orthogonal cover from the RS symbol, thusobtaining a channel estimate value. A channel compensator 1711channel-compensates an ACK/NACK symbol acquired using the channelestimate value. An ACK/NACK de-coverer 1704 decovers an orthogonal coverfrom the ACK/NACK channel. An ACK/NACK decider 1700 decides the value ofthe received ACK/NACK symbols.

FIG. 18 is a flowchart illustrating a reception method of a Node Baccording to an exemplary embodiment of the present invention.

Referring to FIG. 18, the Node B receiver determines whether it issupposed to receive an ACK/NACK symbol in a current subframe from atarget UE in step 1800. If it is, the Node B receiver checks a ZCsequence cyclic shift value and an orthogonal cover index allocated toan ACK/NACK channel of the UE in step 1801. The Node B may havetransmitted the resource information to the UE explicitly or implicitlyby mapping the resource information to the index of a DL data channelassociated with the ACK/NACK channel or the index of a control channelthat delivers scheduling information about the data channel. In step1802, the Node B correlates a received ACK/NACK channel with a ZCsequence based on the resource information. The Node B de-covers theorthogonal covers of the ACK/NACK symbols on a slot basis, in relationto the correlation result in step 1803. In step 1804, the Node B decidesACK/NACK symbols that the UE transmitted on the ACK/NACK channel basedon the de-covered ACK/NACK symbol values.

As is apparent from the above description, the orthogonal coverallocation and hopping technology according to the present inventionadvantageously reduces interference between multiplexed ACK/NACKchannels that use the same cyclically shifted ZC sequence even in a fastmoving environment and randomizes interference between neighbor cells.Therefore, the reception performance of a UL ACK/NACK channel isimproved and cell coverage is expanded.

While the invention has been shown and described with reference tocertain exemplary embodiments of the present invention thereof, it willbe understood by those skilled in the art that various changes in formand details may be made therein without departing from the spirit andscope of the present invention as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. An apparatus for receiving acknowledgment/negative acknowledgment (ACK/NACK) information at a base station (BS) in a wireless communication system, the apparatus comprising: a transmitter configured to transmit data to a user equipment (UE); a controller configured to determine a cyclic shift value and an orthogonal cover Walsh code that are mapped to an ACK/NACK channel index for the UE based on a mapping relationship between a plurality of ACK/NACK channel indexes and a plurality of cyclic shift values and a plurality of orthogonal cover Walsh codes; and a receiver configured to receive ACK/NACK information for the transmitted data using the determined cyclic shift value and orthogonal cover Walsh code, wherein the plurality of orthogonal cover Walsh codes comprises a first orthogonal cover Walsh code [+1 +1 +1 +1], a second orthogonal cover Walsh code [+1 −1 +1 −1], and a third orthogonal cover Walsh code [+1 −1 −1 +1].
 2. The apparatus of claim 1, wherein the ACK/NACK information is received in different frequency bands in first and second slots of a subframe according to the mapping relationship. shift value and orthogonal cover Walsh code, wherein the plurality of orthogonal cover Walsh codes comprises a first orthogonal cover Walsh code [+1 +1 +1 +1], a second orthogonal cover Walsh code [+1 −1 +1 −1], and a third orthogonal cover Walsh code [+1 −1 −1 +1].
 3. The apparatus of claim 1, wherein cross-interference between the first and third orthogonal cover Walsh codes is less than cross-interference between the first and second orthogonal cover Walsh codes.
 4. The apparatus of claim 1, wherein each of the first, second and third orthogonal cover Walsh codes is mapped to different ACK/NACK channel indexes in first and second slots of a subframe according to the mapping relationship.
 5. The apparatus of claim 1, wherein ACK/NACK channel indexes to which the first, second, and third orthogonal cover Walsh codes are mapped in a first slot of a subframe are randomly changed in a second slot of the subframe according to the mapping relationship.
 6. The apparatus of claim 1, wherein the ACK/NACK channel indexes are sequentially allocated to the first, second, and third orthogonal cover Walsh codes according to the mapping relationship, and wherein the ACK/NACK channel indexes are allocated to the first, second, and third orthogonal cover Walsh codes in an ascending order of the cyclic shift values according to the mapping relationship.
 7. An apparatus for transmitting acknowledgment/negative acknowledgment (ACK/NACK) information at a user equipment (UE) in a wireless communication system, the apparatus comprising: a receiver configured to receive data from a base station (BS); a controller configured to acquire a cyclic shift value and an orthogonal cover Walsh code that are mapped to an ACK/NACK channel index for the UE based on a mapping relationship between a plurality of ACK/NACK channel indexes and a plurality of cyclic shift values and a plurality of orthogonal cover Walsh codes; and a transmitter configured to transmit ACK/NACK information for the received data using the acquired cyclic shift value and orthogonal cover Walsh code, wherein the plurality of orthogonal cover Walsh codes comprises a first orthogonal cover Walsh code [+1 +1 +1 +1], a second orthogonal cover Walsh code [+1 −1 +1 −1], and a third orthogonal cover Walsh code [+1 −1 −1 +1].
 8. The apparatus of claim 7, wherein the ACK/NACK information is transmitted in different frequency bands in first and second slots of a subframe according to the mapping relationship.
 9. The apparatus of claim 7, wherein cross-interference between the first and third orthogonal cover Walsh codes is less than cross-interference between the first and second orthogonal cover Walsh codes.
 10. The apparatus of claim 7, wherein each of the first, second and third orthogonal cover Walsh codes is mapped to different ACK/NACK channel indexes in first and second slots of a subframe according to the mapping relationship.
 11. The apparatus of claim 7, wherein ACK/NACK channel indexes to which the first, second, and third orthogonal cover Walsh codes are mapped in a first slot of a subframe are randomly changed in a second slot of the subframe according to the mapping relationship.
 12. The apparatus of claim 7, wherein the ACK/NACK channel indexes are sequentially allocated to the first, second, and third orthogonal cover Walsh codes according to the mapping relationship, and wherein the ACK/NACK channel indexes are allocated to the first, second, and third orthogonal cover Walsh codes in an ascending order of the cyclic shift values according to the mapping relationship.
 13. A method for receiving acknowledgment/negative acknowledgment (ACK/NACK) information at a base station (BS) in a wireless communication system, the method comprising: transmitting data to a user equipment (UE); determining a cyclic shift value and an orthogonal cover Walsh code that are mapped to an ACK/NACK channel index for the UE based on a mapping relationship between a plurality of ACK/NACK channel and a plurality of cyclic shift values and a plurality of orthogonal cover Walsh codes; and receiving ACK/NACK information for the transmitted data using the determined cyclic.
 14. The method of claim 13, wherein the ACK/NACK information is received in different frequency bands in first and second slots of a subframe according to the mapping relationship.
 15. The method of claim 13, wherein cross-interference between the first and third orthogonal cover Walsh codes is less than cross-interference between the first and second orthogonal cover Walsh codes.
 16. The method of claim 13, wherein each of the first, second and third orthogonal cover Walsh codes is mapped to different ACK/NACK channel indexes in first and second slots of a subframe according to the mapping relationship.
 17. The method of claim 13, wherein ACK/NACK channel indexes to which the first, second, and third orthogonal cover Walsh codes are mapped in a first slot of a subframe are randomly changed in a second slot of the subframe according to the mapping relationship.
 18. The method of claim 13, wherein the ACK/NACK channel indexes are sequentially allocated to the first, second, and third orthogonal cover Walsh codes according to the mapping relationship, and wherein the ACK/NACK channel indexes are allocated to the first, second, and third orthogonal cover Walsh codes in an ascending order of the cyclic shift values according to the mapping relationship.
 19. A method for transmitting acknowledgment/negative acknowledgment (ACK/NACK) information at a user equipment (UE) in a wireless communication system, the method comprising: receiving data from a base station (BS); acquiring a cyclic shift value and an orthogonal cover Walsh code that are mapped to an ACK/NACK channel index for the UE based on a mapping relationship between a plurality of ACK/NACK channel indexes and a plurality of cyclic shift values and a plurality of orthogonal cover Walsh codes; and transmitting ACK/NACK information for the received data using the acquired cyclic shift value and orthogonal cover Walsh code, wherein the plurality of orthogonal cover Walsh codes comprises a first orthogonal cover Walsh code [+1 +1 +1 +1], a second orthogonal cover Walsh code [+1 −1 +1 −1], and a third orthogonal cover Walsh code [+1 −1 −1 +1].
 20. The method of claim 19, wherein the ACK/NACK information is transmitted in different frequency bands in first and second slots of a subframe according to the mapping relationship.
 21. The method of claim 19, wherein cross-interference between the first and third orthogonal cover Walsh codes is less than cross-interference between the first and second orthogonal cover Walsh codes.
 22. The method of claim 19, wherein each of the first, second and third orthogonal cover Walsh codes is mapped to different ACK/NACK channel indexes in first and second slots of a subframe according to the mapping relationship.
 23. The method of claim 19, wherein ACK/NACK channel indexes to which the first, second, and third orthogonal cover Walsh codes are mapped in a first slot of a subframe are randomly changed in a second slot of the subframe according to the mapping relationship.
 24. The method of claim 19, wherein the ACK/NACK channel indexes are sequentially allocated to the first, second, and third orthogonal cover Walsh codes according to the mapping relationship, and wherein the ACK/NACK channel indexes are allocated to the first, second, and third orthogonal cover Walsh codes in an ascending order of the cyclic shift values according to the mapping relationship. 